Here is a detailed explanation of each question and option from the ophthalmology MCQ test: 39
1. Magnification of +40D lens is
Correct Answer: B. 10x
Explanation:
Magnification (approximate) by a simple magnifier can be estimated as:
Magnification = Dioptric Power / 4
So, +40D / 4 = 10x magnification
Other Options:
- A. 4x → corresponds to +16D lens.
- C. 20x → would require +80D.
- D. 40x → would require +160D.
2. All are features of convergence spasm except
Correct Answer: C. Mydriasis
Explanation: Convergence spasm involves:
- Excessive convergence
- Accommodation (leading to induced myopia and blurring)
- Miosis (not mydriasis)
Other Options:
- A. Intermittent diplopia → true due to uncoordinated eye movements.
- B. Blurring of vision → true due to overaccommodation.
- D. Induced myopia → true due to accommodative spasm.
3. Which etiologic type of aniseikonia is easily correctable
Correct Answer: A. Optical aniseikonia
Explanation:
- Optical aniseikonia is due to unequal spectacle correction and can be corrected with proper lens design.
- Retinal/Cortical types are due to physical or neurological reasons and harder to manage.
Other Options:
- B. Retinal aniseikonia → caused by retinal diseases (e.g., edema), not easily correctable.
- C. Cortical aniseikonia → neurological origin, not easily correctable.
- D. All are equally easy → incorrect.
4. Optokinetic nystagmus test is a
Correct Answer: D. Resolution acuity test
Explanation:
- It assesses motion detection and the integrity of visual pathways.
- Requires the ability to resolve moving stripes → resolution acuity.
Other Options:
- A. Detection acuity → related to presence/absence of light.
- B. Recognition acuity → involves identifying letters (Snellen).
- C. Direction identification test → incorrect terminology.
5. Arden grating is used for evaluation of
Correct Answer: C. Contrast sensitivity
Explanation:
- Arden gratings are used to measure how well one can detect contrast differences at different spatial frequencies.
Other Options:
- A. Distance vision → measured by Snellen chart.
- B. Colour vision → tested by Ishihara or similar tests.
- D. Diplopia → involves binocular vision testing.
6. Impact-resistance is less for
Correct Answer: A. Glass
Explanation:
- Glass lenses are the most fragile.
- CR39, polycarbonate, and plastic are more shatter-resistant, with polycarbonate being the strongest.
Other Options:
- B. CR39 → better than glass but not as good as polycarbonate.
- C. Polycarbonate → best impact resistance.
- D. Plastic → more impact-resistant than glass.
7. Spherical equivalent of -1.00 + 2.00 x 135
Correct Answer: B. 0.0
Explanation:
Formula:
Spherical Equivalent = Sphere + (Cylinder / 2)
= -1.00 + (+2.00 / 2) = -1.00 + 1.00 = 0.00 D
8. Transpose +4.00 +2.00 x 105
Correct Answer: C. +6.00 -2.00 x 15
Explanation: To transpose:
- Add sphere and cylinder: 4.00 + 2.00 = +6.00
- Change sign of cylinder: -2.00
- Change axis by 90°: 105 → 15
Result: +6.00 -2.00 x 15
9. In hypermetropia far point of the eye is
Correct Answer: D. Virtual and behind the eye
Explanation:
- Hypermetropic (farsighted) eye cannot focus parallel rays on the retina.
- Far point is virtual (not real) and located behind the eye.
Other Options:
- A, B, C are incorrect because the far point is not real and definitely not in front.
10. Distometer is used for measuring
Correct Answer: C. Vertex distance
Explanation:
- Distometer measures the distance from the cornea to the back surface of the lens → vertex distance.
- Important for high prescriptions.
Other Options:
- A. Visual acuity → tested by eye charts.
- B. Power of lens → measured with lensometer.
- D. Contrast sensitivity → measured with Pelli-Robson chart, etc.
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